We are engaged in a coordinated study of the structure and function of the SV40 large T antigen. In progress are experiments designed to assess 1) the role of the two enzymatic activities associated with SV40 T antigen - ATP'ase and protein kinase; 2) the nature of non-origin region SV40 DNA binding sites; 3) the role of large T in the induction of the 55K cellular Tau protein; 4) the structure of the carboxy terminus of this protein isolated from both transformed and lytically infected cells and 5) the sites of T antigen binding in cellular DNA.